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A RCT of Mechanical Ventilation, Directed by Esophageal Pressure Measurements, in Patients With Acute Lung Injury

Brief Summary

The purpose of this study is to see whether esophageal pressure (PES) measurements will allow the investigators to choose the best method of mechanical ventilation in patients with acute lung injury (ALI).

Detailed Description

The current standard of practice for ventilating patients with acute respiratory distress syndrome (ARDS) is the ARDSnet protocol (N Engl J Med 2000; 342:1301-1308) which has been shown to improve survival by limiting tidal volumes and thus preventing over distention of the lungs. However, the lungs can also be damaged by under-inflation during mechanical ventilation, and current practice ignores the effects of chest wall compression of the lungs, which can cause under-inflation. The investigators have observed that a fraction of critically ill patients with apparent ARDS have lung function abnormalities caused by extrinsic compression which can be estimated by PES measurements. Changing ventilator settings to apply normal physiological pressure to the lung has been beneficial in many such patients. This protocol will formally test the clinical utility of PES measurements in patients with ARDS.

This is a randomized controlled trial of therapy directed by esophageal balloon measurements (PES) versus therapy directed by ARDSnet protocol, the current standard of care.

In both groups an esophageal balloon will be placed and baseline measurements recorded. In the EP group the mechanical ventilation settings will be determined based on these measurements. In the control group measurements will be recorded but ventilation will be based in the existing standard of care wich is the ARDSnet low tidal volume ventilation study. measurements will be repeated at 24, 48 and 72 hours or as needed.

Other: Low tidal volume ventilation

Low tidal volume ventilation strategy (ARDSnet)

Other: Transpulmonary pressure-directed ventilation (EPVent)

Transpulmonary pressure-directed ventilation using measurements from the esophageal balloon.

Study Arms

Experimental: EPVent

All patients will have an esophageal balloon placed for the purpose of obtaining transpulmonary pressure measurements. The intervention group will undergo transpulmonary pressure-directed controlled mechanical ventilation using parameters directed by the initial balloon measurements. Driving pressures will be adjusted to maintain a transpulmonary plateau pressure of less then 30. The PEEP setting will be set to achieve a transpulmonary end expiratory pressure of 0. Repeat PES measurements will be done at 24, 48 and 72 hours following the initial measurements. Additional measurements will be taken as clinically indicated. Ventilator management by PES measurements will continue for a period of 72 hours.

Interventions:

Procedure: Placement of an esophageal balloon measurements

Other: Transpulmonary pressure-directed ventilation (EPVent)

Active Comparator: Control

All patients will have an esophageal balloon placed for the purpose of obtaining transpulmonary pressure measurements. The control group will be managed using the low tidal volume strategy laid out by the NIHBLI ARDSnet study. These recommendations include a set tidal volume of 6 ml/ kg. Respiratory rate and PEEP are set to maintain adequate ventilation and oxygenation. These settings will be continued for a period of 72 hours.